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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="log.rationale"></a><a class="link" href="rationale.html" title="Rationale and FAQ">Rationale and FAQ</a>
</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="rationale.html#log.rationale.why_str_lit">Why string literals as scope
      names?</a></span></dt>
<dt><span class="section"><a href="rationale/why_weak_scoped_attributes.html">Why scoped
      attributes don't override existing attributes?</a></span></dt>
<dt><span class="section"><a href="rationale/why_weak_record_ordering.html">Why log records
      are weakly ordered in a multithreaded application?</a></span></dt>
<dt><span class="section"><a href="rationale/why_attribute_manips_dont_affect_filters.html">Why
      attributes set with stream manipulators do not participate in filtering?</a></span></dt>
<dt><span class="section"><a href="rationale/why_not_lazy_streaming.html">Why not using lazy
      streaming?</a></span></dt>
<dt><span class="section"><a href="rationale/why_not_log4j.html">Why not using hierarchy
      of loggers, like in log4j? Why not Boost.Log4j? Etc.</a></span></dt>
<dt><span class="section"><a href="rationale/fork_support.html">Does Boost.Log support process
      forking?</a></span></dt>
<dt><span class="section"><a href="rationale/init_term_support.html">Does Boost.Log support
      logging at process initialization and termination?</a></span></dt>
<dt><span class="section"><a href="rationale/why_crash_on_term.html">Why my application crashes
      on process termination when file sinks are used?</a></span></dt>
<dt><span class="section"><a href="rationale/namespace_mangling.html">Why my application
      fails to link with Boost.Log? What's the fuss about library namespaces?</a></span></dt>
<dt><span class="section"><a href="rationale/msvc_link_fails_lnk1123.html">Why MSVC 2010
      fails to link the library with error LNK1123: failure during conversion to
      COFF: file invalid or corrupt?</a></span></dt>
</dl></div>
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<div class="titlepage"><div><div><h3 class="title">
<a name="log.rationale.why_str_lit"></a><a class="link" href="rationale.html#log.rationale.why_str_lit" title="Why string literals as scope names?">Why string literals as scope
      names?</a>
</h3></div></div></div>
<p>
        One may wonder why not allow arbitrary strings to be used as named scope
        names. The answer is simple: for performance and safety reasons. Named scope
        support functionality has one significant difference from other attribute-related
        features of the library. The scope stack is maintained even when no logging
        is done, so if a function <code class="computeroutput"><span class="identifier">foo</span></code>
        has a <code class="computeroutput"><span class="identifier">BOOST_LOG_FUNCTION</span><span class="special">()</span></code> statement in its body, it is always a slowdown.
        Allowing the scope name to be an arbitrary string would make the slowdown
        significantly greater because of the need to allocate memory and copy the
        string (not to mention that there would be a need to previously format it,
        which also takes its toll).
      </p>
<p>
        Dynamic memory allocation also introduces exception safety issues: the <code class="computeroutput"><span class="identifier">BOOST_LOG_FUNCTION</span><span class="special">()</span></code>
        statement (and alikes) would become a potential source of exceptions. These
        issues would complicate user's code if he wants to solve memory allocation
        problems gracefully.
      </p>
<p>
        One possible alternative solution would be pooling pre-formatted and pre-allocated
        scope names somewhere but this would surely degrade performance even more
        and introduce the problem of detecting when to update or free pooled strings.
      </p>
<p>
        Therefore restricting to string literals seemed to be the optimal decision,
        which reduced dynamic memory usage and provided enough flexibility for common
        needs.
      </p>
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<td align="right"><div class="copyright-footer">Copyright © 2007-2021 Andrey Semashev<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>).
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